The TW200 shares a few of the parts from the BigWheel (forks, rear shock and numerous bits and pieces) but it was different enough from the BigWheels to credit with being a new design. I think all of the Yamaha bikes at this level of production are parts-bin bikes.

Most prominently, the TW200 only has one drive chain, whereas the BW has two differently sized chains and a jackscrew to get power to the wide rear wheel.